Not Applicable.
This invention relates to sheet metal bending machines, and, in particular, to an open center or center-less cheek bender or sheet metal bending machine used to bend small edges or lips on metal pieces, such as are typically used in metal ductwork.
Sheet metal bending machines generally have shafts which drive the element which bends the sheet metal. The use of such shafts prevents such bending machines from being used to bend sheet metal which has a length greater than the length of the opening of the sheet metal bending machine. Hence, the length of sheet metal which can be bent by such current machines is limited by the size of the opening into the machine.
A sheet metal bending machine is provided to form cheek bends in a piece of sheet metal. The bending machine includes a housing having a mouth and a table adjacent the housing mouth. Preferably, the table extends into the mouth to support the sheet metal inside the mouth. A clamping mechanism is provided to hold the sheet metal in place during a bending operation, and a bending mechanism is provided to form a cheek bend in the sheet metal.
The clamping mechanism includes an elongate anvil positioned above the table and which is movable between a raised position in which sheet metal can be inserted in the clamping mechanism and a lowered position in which sheet metal is clamped between said anvil and said table. To move the anvil between its raised to its lowered positions, the clamping mechanism includes an upper link pivotally mounted to the housing and a lower link pivotally connected to a lower end of the upper link. The anvil is operatively and pivotally connected to a lower end of the lower link. The upper and lower links are pivoted relative to each other by a drive (such as a foot pedal operated cable) to be moved from an angled position to a position in which the lower link is substantially aligned with at least a part of the upper link, and in fact, the two links are pivoted to a position slightly over center to lock the anvil in its lowered position. To unlock the links, and allow the anvil to be moved to its raised position, the bending mechanism operatively engages the links to move the links back over center. A spring mechanism then raises the anvil.
In one embodiment, an arm extends from the bending mechanism and a finger extends from the arm. When a bend is complete, the finger engaging the links proximate their pivot point to push the pivot point back to unlock the links. In a second embodiment, the upper link is angled and includes an upper section and a lower section joined at an angle. This angle defines the pivot point for the upper link. An arm extends from the upper link, and is sized and positioned relative to the link upper portion such that when the anvil is in its lowered position, the arm engages the bending mechanism. In this embodiment, the bending mechanism pushes up against the arm when a bending operation is complete to unlock the links and to allow the anvil to return to its raised position.
The bending mechanism comprising an elongate bending bar which is mounted in the housing to be pivotal between a start position in which the bending bar is substantially parallel to the table and a finished position in which the bending bar is pivoted upwardly. The bending bar is pivoted or rotated by a drive. The bending bar is positioned, such that when the bending bar is in its start position and the anvil is in its lowered position, a forward edge of the bending bar is proximate a rearward edge of the anvil. In one embodiment, the bending bar is mounted at its opposite ends to discs. The housing includes openings sized to rotatably receive the discs. The drive including a chain which is operatively connected to the bending bar such that when the chain is pulled, the chain causes the bending bar to pivot. Preferably, the discs do not form a complete circle. In this embodiment, the anvil is horizontally and vertically positioned such that the rear edge of the anvil is approximately aligned with the center of the housing openings.
In another embodiment, the machine includes a curved track which extends around the housing mouth. The track defines a path of travel for the bending bar. Preferably, the bending bar is mounted to a block, and one of the block and said track have a groove, and the other has a rib. The rib is received in the groove.